Blood collection devices with a collection tube for the blood have become known from the EP 0 517 119 B1 and from U.S. Pat. No. 5,458,854 A. The tube, or the blood collection vessel has an integrated, vessel-like blood collection space, with an open upper end and a closed and rounded lower end. The upper end of the vessel is made in one piece with a scoop-shaped lip portion, over whose receiving rim the collected blood can run off into the blood collection space, which compared to the tube has a larger diameter. The upper end of the vessel together with its integral scoop-shaped lip portion can be closed by a cap. During blood collection this is attached to the lower vessel end. In order to be able to fit the blood collection vessel into a standard hospital centrifuge, according to the US patent a complementary vessel is coupled to its bottom. Such a device for collecting small blood amounts is also known from EP 0 072 006 B2. In this construction a scoop-shaped lip portion serving for blood collection or a capillary tube is a fixed component of a cap which can be attached to the blood collecting vessel.
The common feature of these blood collection devices consist in that they have to be precisely positioned in order to capture and transfer the blood into the blood collection vessel, namely positioned exactly with the scoop-shaped lip portion on the location of the puncture on the patient. If the positioning is not precise, the blood cannot be transferred in an orderly manner to the vessel, with the consequence that a fraction of the blood can run off outside along the vessel. The small amount collected in the case of capillary blood is thus considerably reduced. In addition the danger of contamination, or injection [presumed typographical error, it should infection increases considerably for the persons collecting the blood and the laboratory personnel.
In order to eliminate the necessity of precise positioning, thereby simplifying the blood collection, it has become known from U.S. Pat. No. 5,038,794 A to provide capillary tube with a bowl-like funnel, whereby the capillary tube with the funnel or the bowl, is screwed into a collection vessel for the extracted quantity of capillary blood.
From DE 24 39 218 A1 it is known to collect the blood in a specially designed capillary vessel, wherein only the mouthpiece is shaped like a capillary tube, while the remaining portion is widened so that it is possible to insert a micropipette. The end opposite to the mouthpiece, i.e. the large opening of the capillary tube, can be closed by a stopper and, if necessary, the capillary tube can then be inserted into a substantially cylindrical surrounding vessel. Instead of centrifuging the blood after it has been removed from the capillary tube, it is possible to use the capillary vessel directly for centrifugation.
Another problem in the preparation and analysis of very small blood amounts consist in finding such vessels which, on the one hand due to their outer dimensions can fit into the conventional laboratory devices, can be labelled (e.g. with bar codes), and at the same time can insure a certain filling level of the sample which is still good for pipetting or can conveniently be handled. Therefore when vessels with the normal wall thickness and with an outer diameter which can be fitted into the commercially available centrifuges are used, then a capillary blood amount with a volume of one to several droplets has such a low filling level that most of the blood is spread all over the inner vessel surface and almost no sample is available for the analysis. If on the other hand vessels with a smaller diameter are used to insure a sufficient filling level, then these do not fit into the commercially available devices. There is a problem with vessels which in the relevant upper area have adequate dimensions to suit the devices and which taper off downwards, namely that these vessels cannot be provided with commercially available bar code labels. In order to meet these contradictory size requirements, there are commercially available vessels whose outer contours correspond to the commercially available laboratory equipment and whose inner vessel diameter is as small as possible. However these big size differences between the outer and the inner diameter are set off by a relatively very big wall thickness. The manufacture of such vessels leads then to the technical problems well known to the injection molding specialists. Besides the quite expensive injection molding tools required for the production of these vessels with a big wall thickness can be used only for the production of vessels from a single type of plastic material. Since different types of plastic materials react differently with respect to blood or any other sample materials, it is necessary to produce vessels from different types of plastic materials according to the requirements specific to the sample material. This means that each time the production requires the use of a different injection molding tool, which results in high investments.